Typical cables include a conductor, such as a number of copper or aluminum strands, surrounded by an insulation layer. In some instances, the life span of a cable is shortened when water enters the cable and forms micro-voids in the insulation layer. These micro-voids spread throughout the insulation layer in a tree like shape, collections of which are sometimes referred to as water trees.
Water trees are known to form in the insulation layer of electrical cables when voltage is applied to the cable in the presence of water and ions. As water trees grow, they compromise the dielectric properties of the insulation layer until failure occurs. Many large water trees initiate at the site of an imperfection or a contaminant, but contamination is not a necessary condition for water trees to propagate.
Water tree growth can be eliminated or retarded by removing or minimizing the water or ions, or by reducing the voltage stress. Another approach requires the injection of a dielectric enhancement fluid into interstices located between the strands of the cables. However, injecting the dielectric enhancement fluid into the cable is difficult, especially if the cable is to remain in service during treatment. Accordingly, there exists a need for a device which permits a cable to be injected with restorative fluids, such as dielectric enhancement fluids, while permitting the cable to remain in use.